Presently, linear motors are used significantly in automation systems and devices for a variety of applications. For example, these devices are commonly used in the semiconductor wafer inspection processes and wafer lithography systems. While these devices have proven useful in the past, a number of shortcomings associated with these devices have been identified. For example, the generation of resistive heat within the motor forcer coils has proven problematic. Over time, the generation of heat within these systems has been shown to limit motor performance with respect to speed and motor forcer positioning accuracy.
In light of the foregoing, a number of cooling architectures for linear motor systems have been devised. For example, U.S. Pat. Nos. 4,839,545 and 5,783,877, both issued by Chitayat disclose cooling systems for linear motors. Generally, the cooling methods employed in prior art systems are installed in the motor forcer, where the magnetic coils are located. Such cooling is either accomplished using water or other liquids forced through slotted, laminated, or serpentine cooling passages to remove heat. While these systems have proven somewhat successful in the past, a number of shortcomings have been identified. For example, coupling a water source to a movable forcer is complicated and bulky. In addition, the forcer is a movable element, thereby resulting in an increased risk of a leak of fluid.
In response, other manufacturers have devised an alternate cooling method wherein cold air is blown through a nozzle integrated in the magnetic way onto the forcer. While temperature reductions may be obtained using this approach one disadvantage of this system stems from the fact that a temperature gradient is created in the motor environment. The resultant temperature gradient may negatively affect the positioning accuracy of the linear motor.
In light of the foregoing, there is an ongoing need for cooling systems for linear motors.